Impact tool



Patented Feb. 8, 1944 IMPACT troo Lester A. Amtsberg, Cleveland, Ohio, assignor to Chicago Pneumatic Tool Company, New York,

I N. Y., a corporation of New Jersey lorlginai application November 22, 1939, Serial No.

1942. SerialNo. 440.173

3 Claims.

This invention relates to power operated impact tools and more particularly to impact wrenches provided with a clutch which automatically disengages and re-engages to deliver a succession of rotational hammer blows to a driven spindle or tool head. This application is a division of application Serial No. 305,708, filed November 22;

Divided and this application April 23,

asindicated by the arrows 6 in Fig. 1,- and shows the hammer dogs in relation to the anvil.

In the illustrative embodiment, the wrench v comprises an impact clutch enclosed within a 1939, Patent 2,285,638 granted June 9, 1942, which contains claims to a clutch. The present case is directed to a shock absorbing and bearing construction.

Several types of impact wrenches have been used commercially. the clutch being either torque responsive or speed responsive or. as in the case of the parent application aforesaid, responsive to the operation of cam mechanism. All types contain certain parts subjected to re eated shocks of exceedingly great magnitude and therefore are the subject of persistent research to minimize the frequency of breakage and service difliculties.

An object of this invention is the provision of improved means for supporting an impact clutch. particularly the driven spindle thereof. in a wrench housing. Another object is to protect the front end of the wrench housing from the effects of imperfectly balanced impacts delivered to the tool head. A further object is to absorb the shocks transmitted to a steel bushin which supports the tool head. A feature of the invention resides in a resilient sleeve. made of oil resist ng synthetic rubber, and arran ed to provide a firm support for the bushing while maintaining it out of metal-to-metal contact with the housin Other objects and features of the invention will a pear more clearly from the following description taken in connection with the accompanying dr wing and a pended claims.

In the accompanying drawing which illustrates one embodiment of the invention:

Fig. 1 is a longitudinal section of an impact wrench embodying this invention, the rip handle and motor housing being shown partly in elevation and the upper end of the handle being broken w y;

Fig. 2 is a cross section as indicated by the broken line 2-2 in Fig. 1, illustrating particularly the shock absorbing bushing for the front head:

Fig. 3 is an elevational view of the bushing and associated resilient sleeve;

Fig. 4 is a section through the impact clutch. as indicated by the arrows 4 in Fig. 1. and shows the hammer dogs in relation to the driving cam; and Y 1 Fig. 5 is a section through the impact clutch,

clutch housing 9, shown in Fig. 1. This housing is detachably secured in fixed relation to amotor housing l0 and a pistol grip handle II by any suitable means such as the usual arrangement of bolts and flanges (not shown). The front end of the clutch housing is tapered and fluted at l2 to provide anothergrip portion.

A reversible air motor l3 within the motor housing includes a cylinder or cylinder liner I the ends of which abut against end plates IS.

The rear end plate has a flange l6 fitting a recess in the handle member II and a peripheral portion fittingthe motor housing l0. Flange I6 surrounds and supports a ball bearing I! held between end plate I5 and grip handle I l. A similar ball bearing i8 is mounted a flange, projecting forwardly from the front end plate l5. Ball bearingsl1 and I8 respectively support rear and front shafts l9 and integral with and projecting Y from a rotor 2|. The rotor is of cylindrical shape and is arranged coaxially with its shafts and with the clutch housing 9 but eccentric with the cylinder H to provide a crescent shaped chamber between the rotor and cylinder. The rotor is pro-' vided with a plurality of radial slots in which blades 22 are mounted for movement with their outer edges in scraping contact with the cylinder to divide the crescent shapedchamber into a series of pockets between the inlet and exhaust ends. A reverse lever 23 controls the direction of flow of compressed air and hence the direction of rotation of motor l3. l

Positioned centrally of the clutch housing is a rotatable tool head or driven spindle 25 having an elongated shank 28 and having an anvil portion comprising jaws 27 adapted to receive rotational impacts as hereinafter described. Under theusual operating conditions these impacts tend to misalign the tool head axis, as it is practically impossible to manufacture an impact clutch in which both anvil jaws are always struck with the same force at exactly the same instant. In prior devices the continual radial vibration of the tool head due to imperfectly balanced impacts gradually enlarge the bore on the front end 0; the clutch housing and in time caused the housing to crack. This defect has been overcome in the present invention by the use of a'novel means for supporting the tool head.

Shank 26 of the tool head is supported with a rotating fit in a steel bushing 29. A resilient sleeve madeof oil resisting rubber surrounds the bushing and is vulcanized to the outer surface thereof. A synthetic rubber-like material known to the trade as Neoprene is suitable for this purpose. For a description of its composition and properties, reference is made to. Carothers and Collins U. S. Patent 1,950,432 granted March 13, 1934. The synthetic rubber sleeve 30 has a press fit with a counter-bore 3| near the front end of clutch housing 9 and the lower end of the sleeve rests on a shoulder extending between the counterbore and a bore 32. The bore last mentioned is slightly larger in diameter than the steel bushing 29 and in operation metal-to-metal contact between the bushing and housing is avoided. The upper end of the resilient sleeve terminates at an annular flange 33 supporting a similar flange on the steel bushing and seated on a shoulder of the clutch housing.

Lubrication of the interior of the steel bushing 29 may be effected by removing a grease plug 35 from a threaded opening in the clutch housing which provides access to an annular groove 36 formed around the synthetic rubber sleeve 30. Complementary. registering ports in the sleeve and bushing admit lubricant to an annular groove 31 formed on the inner surface of the steel bushing.

The rear end of the tool head 25 is supported in axial alignment with the steel bushing 29 and with rotor shaft 20 by means which include a pilot shaft 39 seated in complementary recesses in the rotor shaft 20 and tool head.

The impact clutch comprises a hammer assembly which surrounds the anvil and is supported at the front and rear ends of theanvil for revolution about the axis of the latter, the arrangement resembling a squirrel cage. The anvil jaws 21 may be designed at any desired length in an axial direction. The hammer assembly extends between two similarly constructed end plates which constitute carriers by which the assembly is revolubly supported. Rear carrier 40 is mounted for oscillatory movement about a bearing surface provided on the rear-end of a driving cam 4| splined to the rotor driving shaft 20. A bearing spacer 42 abuts against the rotor bearing l8 at its rear end and the driving cam 4| and hammer carrier 40 at its front end to secure the cam and carrier against rearward axial movement. A thrust plate 43 surrounding the pilot shaft 39 engages the front end of the driving cam and the rear face of the tool head 25 permitting relative rotation therebetween. Forward movement of the carrier 40 is prevented by engagement by cam projections 44 radiating from the front' end of the cam.4|. The front end plate or front carrier 45 for the hammer assembly is mounted for rotary movement relative to the shank 26 of the tool head 25, a. bushing 46 being interposed between the carrier and the tool head. The rear and front ends of the bushing 46 and front carrier 45 abut I against a shank spacer 41 and a thrust washer 48 respectively. The shank spacer engages the front of the anvil jaws 21 while the thrust washer seats on the steel bushing 29 whereby the tool head 25 and carriers 40 and 45 are supported against axial thrusts.

A .pair of heavyhammer dogs 50, similarly constructed and arranged, are supported for oscil latory movement about pivot pins 5| which extend through openings in the dogs and carriers. the heads of the pivot pins being retained by the thrust washer 48. A pair of bolts 52 are arranged and each bolt is surrounded by aspacer sleeve 53 whose ends abut against the carrier plates. The bolts and pivot pins are evenly spaced about the axis of revolution. as illustrated in Fig. 5 and extend parallel to the axis of revolution and cooperate with each other to hold the carriers rigidly in fixed relation to each other and to the pivot pins. The radial arms 44 on the driving cam 4| project into driving engagement with recesses 55 at the rear end of the hammer dogs 50.

The front end of the tool head shank 26 terminates at a socket engaging projection 51 of polygonal cross section fitting a correspondingly shaped opening 58 in wrench socket 58 for the driven bolt or nut N. The end of the tool head and the socket-have registering transverse apertures and BI which receive a locking pin 62. The pin is preferably a rigid cylindrical rod and serves to prevent accidental detachment of the socket from the tool head projection 51 but permits ready removal and replacement of the socket when that is desired. As it is not feasible to make a substantially perfect fit between the socket 59 and the tool head projection 51, there is a slight amount of lost motion between these parts when a torsional impact is transmitted. In order that the entire blow may be delivered to the wrench socket direct and not through the locking pin, which might cause the latter to shear or become deformed. the pin is so mounted that it normally engages only one of the two elements that it looks, for example, the tool head projection 51. This is accomplished by making the apertures 6| in the socket larger than the aperture 60 which fits the pin 62. A simple expedient is employed for preventing accidental movement of the looking pin 62 lengthwise of its associated bore 60. According to the present arrangement the looking pin is secured by means of a retainer ring 63 of elastic material surrounding the pin and frictionally engaging a cylindrical surface on the socket member 59. It has been found that a rub- 'ber band of ordinary construction whose diameter when untensioned is less than that of the cylindrical portion of the socket is admirably suited for this purpose and that such a retainer does not become displaced under vibration as it has little weight and a large amount of friction, but is adapted to be shifted manually and readily upon further stretching.

In operation, the throttle lever (not shown) and reverse lever 23'are set to admit air to the motor l3 to drive the socket 59 in a clockwise direction, looking forward. The driving cam 4|, having a direct connection with'the rotor shaft 20, delivers a force to the hammer dog 50 in such a direction that the dogs have imparted to them a motion of revolution about the axis of tool head 25 and a component of force which tends to declutch them relative to the anvil jaws 21 on the tool head. The dogs are pivotally mounted on a carrier assembly which includes the carrier plates 40 and 45 and the pivot pins 5| and this assembly is carried with the dogs as they revolve. The dogs 50 are guided for rocking movement about pivot pins 5| due to camming engagement of the convex inner face of the dog with the anvil jaw to pass through openings in the carrier plates 7 21. Upon completion of the rocking movement the dogs 50 are meshed with the anvil jaws 21. If the resistance to rotation of the driven nut N is relatively slight, the clutch parts may remain for a considerable period in meshed relation, all parts revolving in unison due to friction between the dogs 50 and anvil 21 and between the dogs 50 and their pivot pins 5|.

in mesh are overcome by the declutching force set up by the driving cam M on the hammer dog and the dogs are rocked in a releasing direction. As soon as the-dogs are declutched, the driving unit is relieved of its load and accelerates to accumulate kinetic energy during a half turn of the motor after which the driving unit is arrested with an impact. A succession of impacts continues as long as the op rator holds the wrench socket in engagement with the torque resisting nut and continues the supply of air to the motor.

If the resistance to rotation is moderate the dogs will be declutched before the driving unit comes to a complete rest relative to the wrench casing 9 although the driving unit is arrested at the time of each impact relative to the tool head 25.

Preferably the shank 2t oftool head 2-5 is of sufficient axial length that advantage may be taken of the torsional elasticity of the steel. Thus, when a rotational hammer blow is delivered to the rear end of the tool head and the front with the housing, thereby preventing the delivery of hammer blows tending to crack the housing, said steel bushing being flared outwardly at its rear end to provide an annular flange subjected to forward axial thrusts, the rear end of the resilient sleeve having a complementary flange interposed between the steel flange and the housing to absorb such axial thrusts, the,

periphery of the sleeve forwardly of the lastmentioned flange being substantially cylindrical whereby the sleeve and bushing may be inserted end is held in engagement with a frozen nut N,

the tool head twists slightly. Upon termination of the impact, the shank unwinds causing the hammer dogs 50, carrier members 40, t5 and 5!, driving cam M and rotor 2! to rebound as a unit in a direction opposite to the rotary impact. The rebound acts to momentarilyrelieve contact pressure between the impact surfaces on the dogs and anvil thereby facilitating declutching and reducing the rubbing action of the impact surfaces over each other. I

From the foregoing description it is apparent that the invention permits the tool head to yield in response to force's moving it out of axial alignment with the supporting portion of the housing and thereby protects the parts to which impacts are transmitted.

a sleeve of rubber like material surrounding the' steel bushing and vulcanized thereto, said resilient sleeve being seated in the front end of the housing with a press flt and positioned to maintain the steel bushing out of metal-to-metal contact as a unit into operative relation with the housing.

2. An impact wrench comprising a housing, a rotatable tool head in the housing and projecting from the front end thereof, an anvil portion on the tool head near its rear end positioned to receive rotational impacts tending to shift the axis of the tool head with a vibratory action, a rotatable hammer assembly surrounding the tool head for delivering such impacts, said hammer assembly having a bearing portion supported on the tool head in front of the anvil portion, said tool head having sumcient axial length to permit a slight torsioning of the tool head during the delivery of an impact, bearing means supporting the rear extremity of the tool head, and a front bearing for supporting the tool head near the front end of the housing, said front bearing being resilient to permit a slight lateral movement of the tool head during the delivery of an impact.

3. An impact wrench comprising a housing, a rotatable tool head in the housing having an anvil portion near its rear end positioned to receive rotational impacts tending to shift the axis of the tool head with a vibratory action, a hammer assembly for delivering such impacts and including 1 of destructive impacts to the housing.

LESTERAA MTSBERG. 

